Design of a water treatment system for beneficial use of the produced water in a gas field in Bangladesh

Abstract

Produced water is water trapped in underground formations that is brought to the surface along with oil or gas. It is by far the largest volume byproduct or waste stream associated with oil and gas production. Produced water handling has been an issue of concern for oil and gas producers as it is one of the major factors that cause abandonment of the producing well. The development of effective produced water management strategies poses a big challenge to the oil and gas industry today. The conversion of produced water into irrigation or fresh water provides a cost-effective tool to handle excessive amounts of the produced water. There are more than 150 methods for produced water treatment. In this research, we proposed on-site produced water treatment units configured to achieve maximum processing throughput for Bangladesh. We tested the produced water sample collected from a Gas field in Bangladesh in BASF Bangladesh Ltd. construction chemical Lab. The lab test result showing that the Dissolved oil, EC, TDS, Na+, Cl-, HCO3- , COD, Ca2+, and other parameters of produced water are much higher than the acceptable limit define by Environment and Forest Ministry of Bangladesh. We also studied various advanced separation techniques to remove oil and dissolved solids from the produced water. We selected media filtration as the oil removing technique and Reverse Osmosis (RO) as the dissolved solids removing technique along with three stage separators as being the best for Bangladesh based on produced water property. The study results show that the media filtration remove more than 90% of the oil and grease and water recovery nearly 100%. The RO units remove more than 95% of total dissolved solids from the produced water and it is the most used technology in the world (> 60% of worldwide seawater desalination installed capacity). The proper integration and configuration of media filtration and RO units can provide up to 80% efficiency for a processing throughput of 6-8 gallons per minute of produced water. Finally a water treatment system designed considering a gas field producing 600 bbl equals 95400 litters water per day. The system is flexible and can be modified for the applications such as rangeland restoration, reservoir recharge and agricultural use and household use.